This invention relates to a method for the production of a heat-sensitive record material and more particularly to an improved surface treatment of a heat-sensitive record material.
The heat-sensitive recording system is generally based on the principle of heating a thermal recording head (hereinafter referred to simply as "head") in response to an input signal, whereby a colorless chromogenic material and a color acceptor on the record material sheet contacted with said head are melted and contacted with each other to provide a color image. It has a recording speed matching with the amount of information in a band carried by a telephone circuit and is of the primary color developing system not requiring the developing or fixing process, and because of little wear of the head, it is being rapidly applied to information equipment such as printers and facsimile machines.
Particularly, with the recent enormously increasing amount of information, development has been made from the so-called low speed machines such as facsimile machines in which the record time required for one page of paper size A4 is about 6 minutes to the high speed machines such as facsimile machines of about 1 minute in the same definition and the super high speed machines having much higher recording speeds, and with such increase in the processing speed of recording apparatuses, record sheets used herewith are being improved in various respects. Among them the smoothing treatment of the record layer surface has been studied and investigated as one of the most important factors in that it increases the degree of contact between the head and the record layer surface to facilitate heat transfer. If, however, a high speed record material sheet having a record layer with a composition designed to increase recording sensitivity is treated by any one of conventional supercalenders and other various smoothing devices incorporated to coaters, the record layer surface, though highly smoothed, is suffered from incidental fogging and the degree of color brightness of the recording layer is greatly lowered. Thus, the present situation is that it is inevitable to perform either a light degree of surface treatment at the sacrifice of smoothness or a smoothing treatment at the sacrifice of the degree of brightness of the record layer surface.
In view of such situation, we have made an intensive study in order to develop a method of properly smoothing the record layer surface without causing fogging. Particularly, after an extensive investigation of the construction and material of the rolls defining the pressing nip of the smoothing apparatus, the operating conditions of the smoothing apparatus and the composition of the recording layer, we have found that the use of a specific elastic roll having a softness which is undreamed of in the case of the conventional pressing and smoothing apparatus makes it possible to effect a smoothing treatment of the record layer surface which is desirable to imparting high speed recordability to the record layer surface without involving unevenness of color development, which finding has led to the achievement of the present invention.
The principal object of the invention is to provide an improved method of the surface treatment of a heat-sensitive record material in which a heat-sensitive record material having excellent high speed recordability can be efficiently produced without causing fogging.
The other objects and advantages of the invention will become apparent from the following detailed description.